Abstract
To reveal the structural stabilities and transformation mechanism of rhynchophylline (RIN) and isorhynchophylline (IRN), HPLC and UPLC-Q-TOF-MS method were developed for the qualitative and quantitative analysis of the conversion rate. The method was validated for linearity, inter- and intra-day precisions, repeatability and stability. All the quantitative determination method validation results were satisfactory. Under the optimized chromatographic conditions, the effect of various heat temperatures, retention time, and solvent polarities on conversion rate and equilibrium were systematically investigated for the first time. Besides, a model relating the retention yield value and time-temperature was built to predict the t0.5 and Ea of the conversion rate by the Arrhenius equation. The experimental results proved to be in good accordance with the predicted values. Furthermore, UPLC-Q-TOF-MS analysis was performed to verify the transformation mechanism and provide valuable information for stability analysis of the conversion products.
Highlights
Uncaria rhynchophylla (Miq.) known as Gou-teng in Chinese, is one of the most famous herbal resources, extensively used as a traditional medicine in China, India, Korea, and other Southeast Asian countries for prevention and treatment of hypertension, cardiac arrhythmia, anxiety, convulsions and epilepsy [1,2]
To study the conversion rate of RIN and IRN, the experimental results were analyzed by the Arrhenius equation
The chemical structures of RIN and IRN correspond to a pair of diastereoisomeric C2 oxindole alkaloids, whose only difference is the configuration at C7, (Figure 1)
Summary
Uncaria rhynchophylla (Miq.) known as Gou-teng in Chinese, is one of the most famous herbal resources, extensively used as a traditional medicine in China, India, Korea, and other Southeast Asian countries for prevention and treatment of hypertension, cardiac arrhythmia, anxiety, convulsions and epilepsy [1,2]. RIN and IRN are often used as chemical markers for the quality control of U. rhynchophylla. According to the research, the analysis performance varied between lots, and widely between similar methods, which may seriously affect the subsequent quality control of U. rhynchophylla. In order to obtain information to control the quality of the preparation of U. rhynchophylla and provide valuable information for industrial purposes, the stabilities and transformation mechanism of RIN and IRN were investigated. There are no studies about the stability and conversion rates between RIN and IRN. The effects of various temperatures, reaction times, and solvent polarities were investigated. UPLC-Q-TOF-MS analysis was performed to verify the transformation mechanism and provide valuable information for the analysis of the stability of the conversion products
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